Question:easy

The value of \(\displaystyle\int_{0}^{\pi/4}\sin^{3}2x\cos2x\,dx\) is:

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Substitute u = sin2x.
Updated On: Sep 24, 2026
  • \(\dfrac12\)
  • \(\dfrac14\)
  • \(\dfrac18\)
  • \(\dfrac1{16}\)
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Using a reduction identity:
\(\sin^3 2x\cos2x=\dfrac14\sin^2(2x)\cdot\sin(4x)\)... instead, directly integrate by recognizing the power rule for \(\sin2x\).

Step 2: Direct antiderivative:
\(\displaystyle\int\sin^{3}2x\cos2x\,dx=\frac{\sin^{4}2x}{8}+C\), obtained since \(\frac{d}{dx}\sin^4(2x)=4\sin^3(2x)\cos(2x)\cdot2=8\sin^3(2x)\cos2x\).

Step 3: Evaluating between the limits:
\(\Big[\frac{\sin^4 2x}{8}\Big]_0^{\pi/4}=\frac{1}{8}-0\).

Final Answer:
\[ \boxed{\dfrac18} \]
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